Assigistoe to the



(No Model.)

- T. N. VAIL.

- ELECTRIC SWITCH BOARD.

No. 330,644. Patented Nov. 17, 1885.

UNTTE STATES PATENT EEI AMERICAN BELL TELEPHONE ELECTRlC SWlTGH BOAl-"i COMPANY, OF SAME PLACE.

'SPECIFICATEQN terrain part of Letters Patent No. 330,644 dated i'loveinber 17 1885.

Application filed July '7, 1885.

To all whom it; may concern:

Be it known that l, THEODORE N. VAIL, residing at Boston, in the county of Suffolk and State of Massachusetts, have invented certain Improvements in Electric Switch- Boards, of which the following is a specification.

My invention relates to electrical switchboards of that class wherein the connectionstrips whereby any two circuits are or may be united are represented by sheets or plates of metal insulated one from another, while the several line-circuits are attached to and repre sented by smaller plates, one for each circuit, these latter being secured to the surface of a plate of non-conducting material, which surmounts the whole. The connections in such switchboards are made by the insertion of plugs made in pairs of difierent lengths, each separate pair of plugs being of the precise length requisite to make contact with one of the connection-plates and no other,while, irrespective of length, all the pairs are adapted to make contact with the smaller or line plate. Such switch-boards are adapted by virtue of their peculiar construction to he placed horizontally, and advantageously operated by per sons stationed at its several sides.

The object of my present invention, briefly stated, is to provide a switch-board which, with great economy in construction, shall be durable, simple in operation, and much more convenient and commodious than those in common use. I have heretofore obtained Letters Patent of the United States No. 255,056, bearing date March 1 L,1882, and No. 296,253, bearing date April 1,1884, which recite and claim certain inventions and improvements in switch-boards of this class, consisting, first, in the use of alternating very thin connecting and insulating plates made operative by causing a portion only of each plate to project into the plug hole, the plug being provided, also, with a corresponding projection arranged to meet the same and make contact therewith; and, secondly, in the substitution for the said connecting-plates of conducting strips,bars, or wires, the several strips of each layer being all connected together, so that they collectively constitute a practical equivalent of acomplete and continuous plate.

Serial No. 170,849. (No model.)

My present invention is an improvement and modification on the foregoing patents; and it consists in the use of wires stretched tight alone, in lieu of any other conneetionplates whatsoever in the combination, with such wires, of suitable stretching and straining devices, and in dispensing altogether with the alternating nonconducting plates, using in lieu thereof a space of dry air only. The advantages of this construction are obvious. A better connection can be made when wires only are employed, while they maintain rigidity under circumstances where fiat strips would yield. They can,moreover,be tightened with a greater degree .of ease. Owing to the absence of the intervening non-conducting plates, the thickness of the mass may be reduced and many of the connecting pins or plugs correspondingly shortened, while the substitution of dry air for the material and moresolid plates whichI have heretofore employed is otherwise advantageous, seeing that dry air, while one of the best of insulators, (being the first on the list given in Gulleys Manual of Telegraphy,)l1as also a lower specific inductive capacity than nearly every other insulator.

In the drawings which illustrate my invention, Figure 1 is a plan view of the upper surface of the switchboard. Fig. 2 is a partial vertical section on the line 00 00 of Fig. 1. Fig. 3 is a horizontal cross-section of the switch-board, showing Uhe several connectingwires. Fi 4 is a detail view showing a pair of plug-connectors inserted, one being in place and the other about to be turned into contact with the wire; and Fig. 5 indicates the stretching apparatus and the mode in which it is employed.

In constructing the switch-board, I provide a base-board, and upon it I construct a suitable frame, O, by means of which the wires w, representing the connecting-plates, are sup ported, the consecutive layers of wires being transversely disposed with reference to the layer immediately adjacent on either side. As in my prior patent of April 1, 1884, hereinbefore cited, the several wires are so fixed that each one extends across an arc of the series of plug-holes which it crosses, so as to form a chord of the said are, and each hole, in

virtue of the four chords it thus contains, is practically square. The several connectingplugs are in like manner made in pairs, to reach through the mass and to connect the line-plate with any desired connecting-wire, while all of the said connecting-wires on the same horizontal plane are connected together so as to constitute an individual electrical conductor separate from all others and complete in itself, and, as shown in the same patent, (to which reference may be made,) the several connecting-conductors thus formed may, by suitable wires or other continuations, be brought to the surface of the board and combined with manipulating devices, such as the centralstation telephones and signaling apparatus. The walls 0 of the frame are made necessary by the fact that the connecting-wires w are to be stretched taut, all forms heretofore having employed connecting devices merely laid upon the mass without stretching devices, and held in place merely by the pressure of the various layers of the board, aided by the clamping-bolts. The several connecting-wires are arranged in series of four, w, w,w and w, as shown, the immediately adjacent neighbor of each wire on either side being transversely disposed with reference to the said wire. Any desired number of these series of four may be incorporated in a single switchboard, this feature being only governed by the necessity of keeping the length of the connecting-plugs down to a practical limit. The several wires of each layer are of sufficient length to extend through holes bored for the purpose in the walls of the switch-board, the wires 20 and 10 being supported by the walls 0 and 0 While the transverse wires w and w are similarly sup ported by O and O. Non-conducting supporting cleats or partitions M, having holes through which the wires are passed, are provided, crossing the entire superstructure from side to side, to prevent the wires from sagging and making undesigned contacts with one another. Any requisite number of such partitions may be provided, as the size of the switch-board may require.

I do not provide any interposed non-conducting plates between the different layers of wires, these being at all times out of contact with one another, and the airis consequently the onlyinterposed dielectric. YVhen as many layers of connecting-wires are arranged in place as are for any individual switch required, the non-conducting top or covering plate A is superposed over the structure, and may be screwed thereto by the bolts B at the corners and at as many intermediate points as may be necessary. Upon this plate A,I place in a manner well understood the several lineplates 1 each of which is at all times in contact with and represents a main line, and is perforated for the reception of the connectingplug 1). The arrangement of the connectingwires with respect to each hole is indicated by the four lines forming a square therein. The plug-connectors are formed with a cam projection at their lower extremities, and when the plug is to be inserted in the holethe cam will be so disposed as to pass through the hole at one of its corners until the designed connecting-wire is reached, when the plug is slightly turned round, and the cam thereupon slides under the said wire, making contact therewith and uniting the said wire to the line plate. To connect any two wires together,two plugs of the same length are chosen and caused to make contact with the same wire.

I find it very convenient to bring the linewires to the switch-board by means of multiple cables f, which are led along the upper surface of the board, and from which the several line wires 1, 2, 3, and 4, &c., are branched to their several line-plates. The cables may alternatively be carried below the surface of the plate, and the wires reaching the line-plates may be attached to them, either through the instruinentality of screw-posts 8, as shown in Fig. 2, or may simply be attached to the side of the plate by soldering. The wires of each layer are connected together by outside wires, a Z) c d, so that all the wires of each layer combine to form of that layer a sin gle connecting link accessible to any lineplate of the board. Each wire is maintained taut by the screw end and nut e, and to the end that, in the operation of tightening, 11o undue strain will fall upon the nuts and screwthread, I prefer to bend the ends 0 of the wires after placing the nut thereon, and I provide a special tool, T, which, being inserted below the end 0, is enabled to pull out the wires until they are completely taut, after which the nuts are screwed up and the wires are maintained at their proper degree of strain.

Having thus described my invention, I claim 1. In an electric switch-board, the combina tion of connecting-wires stretched taut and arranged in layers, as described, each alternate layer being transversely disposed with respect to the layers immediately above or below the same, the line-plates fixed to a nonconducting covering-plate, each of the said line-plates being perforated for the reception of a plug-connector, and placed over an intersection-point of the several wire layers, and a series of plug-connectors provided in pairs of varying length, the said plugs being adapted for insertion through the line-plates and to connect the said line-plate with any desired one of the connecting-wires, in the manner described.

2. An electric switchboard consisting of a non-conducting frame, a series of superposed layers of horizontally -arranged connectingwires stretched taut therein, to serve as connecting-links between any two main lines, the said layers being each in different horizontal planes and insulated from one another by air only, a non-conducting plate surrounding the whole, a series of perforated line'plates, each representing a main line, mounted on the said non-conductingplate, and a series of pairs of plug-connectors, each pair being adapted to extend through the line-plates and to make contact with one of the layers of connectingwires, as and for the purposes described.

3. The combination, in-a horizontal electric switchboard, of the connectingwires, arranged as herein described, and fastening devicessuch as screws and nutsas indicated, for detachably securing said wires to the frame of the switch-board, so that they can be tightened when necessary.

4. The combination, in a horizontal electric switchboard, of the connectingwires arranged in horizontal layers of different planes, each alternate layer being transverse to the adjacent layers, and the several wires being provided with hooked ends, and the fastening devices detachably securing .the ends of said wires to the frame of the switch-board, so that they can be tightened when necessary, substantially as described.

perforated for the reception of a plug-cono nector, affixed to and supported by the said plate, and the stretched wires arranged in transversely-disposed horizontal layers in the dry-air space within the in closing-case, so that one wire of each layer crosses an arc of the 5 circle of each of theline-plates, and plug-holes, as described, whereby each layer of wires is caused to serve as a connecting-plate and may by suitable plug-connectors be united.

with any of the said line-plates, substantially 0 as hereinbefore described. a

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 27th day of June, 1885.

THEO. N. VAIL.

\Vitnesses:

Tnos. D. LOOKWOOD, GEO. WILLIs PIERCE. 

